mn10300-watchdog.c

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/* MN10300 Watchdog timer
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 * - Derived from arch/i386/kernel/nmi.c
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/kernel_stat.h>
#include <linux/nmi.h>
#include <asm/processor.h>
#include <linux/atomic.h>
#include <asm/intctl-regs.h>
#include <asm/rtc-regs.h>
#include <asm/div64.h>
#include <asm/smp.h>
#include <asm/gdb-stub.h>
#include <proc/clock.h>

static DEFINE_SPINLOCK(watchdog_print_lock);
static unsigned int watchdog;
static unsigned int watchdog_hz = 1;
unsigned int watchdog_alert_counter[NR_CPUS];

EXPORT_SYMBOL(touch_nmi_watchdog);

/*
 * the best way to detect whether a CPU has a 'hard lockup' problem
 * is to check its timer makes IRQ counts. If they are not
 * changing then that CPU has some problem.
 *
 * since NMIs dont listen to _any_ locks, we have to be extremely
 * careful not to rely on unsafe variables. The printk might lock
 * up though, so we have to break up any console locks first ...
 * [when there will be more tty-related locks, break them up
 *  here too!]
 */
static unsigned int last_irq_sums[NR_CPUS];

int __init check_watchdog(void)
{
    irq_cpustat_t tmp[1];

    printk(KERN_INFO "Testing Watchdog... ");

    memcpy(tmp, irq_stat, sizeof(tmp));
    local_irq_enable();
    mdelay((10 * 1000) / watchdog_hz); /* wait 10 ticks */
    local_irq_disable();

    if (nmi_count(0) - tmp[0].__nmi_count <= 5) {
        printk(KERN_WARNING "CPU#%d: Watchdog appears to be stuck!\n",
               0);
        return -1;
    }

    printk(KERN_INFO "OK.\n");

    /* now that we know it works we can reduce NMI frequency to something
     * more reasonable; makes a difference in some configs
     */
    watchdog_hz = 1;

    return 0;
}

static int __init setup_watchdog(char *str)
{
    unsigned tmp;
    int opt;
    u8 ctr;

    get_option(&str, &opt);
    if (opt != 1)
        return 0;

    watchdog = opt;
    if (watchdog) {
        set_intr_stub(EXCEP_WDT, watchdog_handler);
        ctr = WDCTR_WDCK_65536th;
        WDCTR = WDCTR_WDRST | ctr;
        WDCTR = ctr;
        tmp = WDCTR;

        tmp = __muldiv64u(1 << (16 + ctr * 2), 1000000, MN10300_WDCLK);
        tmp = 1000000000 / tmp;
        watchdog_hz = (tmp + 500) / 1000;
    }

    return 1;
}

__setup("watchdog=", setup_watchdog);

void __init watchdog_go(void)
{
    u8 wdt;

    if (watchdog) {
        printk(KERN_INFO "Watchdog: running at %uHz\n", watchdog_hz);
        wdt = WDCTR & ~WDCTR_WDCNE;
        WDCTR = wdt | WDCTR_WDRST;
        wdt = WDCTR;
        WDCTR = wdt | WDCTR_WDCNE;
        wdt = WDCTR;

        check_watchdog();
    }
}

#ifdef CONFIG_SMP
static void watchdog_dump_register(void *dummy)
{
    printk(KERN_ERR "--- Register Dump (CPU%d) ---\n", CPUID);
    show_registers(current_frame());
}
#endif

asmlinkage
void watchdog_interrupt(struct pt_regs *regs, enum exception_code excep)
{
    /*
     * Since current-> is always on the stack, and we always switch
     * the stack NMI-atomically, it's safe to use smp_processor_id().
     */
    int sum, cpu;
    int irq = NMIIRQ;
    u8 wdt, tmp;

    wdt = WDCTR & ~WDCTR_WDCNE;
    WDCTR = wdt;
    tmp = WDCTR;
    NMICR = NMICR_WDIF;

    nmi_count(smp_processor_id())++;
    kstat_incr_irqs_this_cpu(irq, irq_to_desc(irq));

    for_each_online_cpu(cpu) {

        sum = irq_stat[cpu].__irq_count;

        if ((last_irq_sums[cpu] == sum)
#if defined(CONFIG_GDBSTUB) && defined(CONFIG_SMP)
            && !(CHK_GDBSTUB_BUSY()
                 || atomic_read(&cpu_doing_single_step))
#endif
            ) {
            /*
             * Ayiee, looks like this CPU is stuck ...
             * wait a few IRQs (5 seconds) before doing the oops ...
             */
            watchdog_alert_counter[cpu]++;
            if (watchdog_alert_counter[cpu] == 5 * watchdog_hz) {
                spin_lock(&watchdog_print_lock);
                /*
                 * We are in trouble anyway, lets at least try
                 * to get a message out.
                 */
                bust_spinlocks(1);
                printk(KERN_ERR
                       "NMI Watchdog detected LOCKUP on CPU%d,"
                       " pc %08lx, registers:\n",
                       cpu, regs->pc);
#ifdef CONFIG_SMP
                printk(KERN_ERR
                       "--- Register Dump (CPU%d) ---\n",
                       CPUID);
#endif
                show_registers(regs);
#ifdef CONFIG_SMP
                smp_nmi_call_function(watchdog_dump_register,
                    NULL, 1);
#endif
                printk(KERN_NOTICE "console shuts up ...\n");
                console_silent();
                spin_unlock(&watchdog_print_lock);
                bust_spinlocks(0);
#ifdef CONFIG_GDBSTUB
                if (CHK_GDBSTUB_BUSY_AND_ACTIVE())
                    gdbstub_exception(regs, excep);
                else
                    gdbstub_intercept(regs, excep);
#endif
                do_exit(SIGSEGV);
            }
        } else {
            last_irq_sums[cpu] = sum;
            watchdog_alert_counter[cpu] = 0;
        }
    }

    WDCTR = wdt | WDCTR_WDRST;
    tmp = WDCTR;
    WDCTR = wdt | WDCTR_WDCNE;
    tmp = WDCTR;
}